KR100718793B1 - Organic electroluminescent polymers having 9,9-di3,3'-bicarbazyl-2,7-fluorenyl unit and the electroluminescent device prepared using the same - Google Patents

Abstract

The present invention relates to an organic electroluminescent molecule containing 9,9-di (3,3'-bicarbazyl) -2,7-fluorenyl unit and an electroluminescent device using the same. 9,9-di (3,3'-bicarbazyl, which can be used as a blue electroluminescent polymer and host material by introducing a 3,3'-bicarbazyl (3,3 ') group in the 9-position The present invention relates to an organic electroluminescent molecule containing 2-2,7-fluorenyl unit and an electroluminescent device using the same. The electro-adhesive molecules according to the present invention have high solubility and high thermal stability, and the hole transport property is improved to show high luminous efficiency.

Light emitting polymer, light emitting device, blue light emission, quantum efficiency, fluorene, fluorenyl

Description

Organic electroluminescent molecules containing 9,9-di (3,3'-bicarbazyl) -2,7-fluorenyl units and electroluminescent devices using the same {0,9-di (3,3 ') -bicarbazyl) -2,7-fluorenyl unit and the electroluminescent device prepared using the same}

1 is a cross-sectional view showing a structure of a general organic electroluminescent device manufactured from a substrate / anode / hole transport layer / light emitting layer / electron transport layer / cathode.

Figure 2 is a reaction schematic showing the manufacturing process of the electro-molecular advertising molecules represented by the formula (2) of the present invention.

3 is a ¹ H-NMR spectrum of Compound (4) prepared according to Example 4 of the present invention.

4 is a ¹ H-NMR spectrum of the compound represented by Chemical Formula 2 prepared according to Example 5 of the present invention.

5 is a fluorescence spectrum in the chloroform solution of the compound represented by the formula (2) prepared according to Example 5 of the present invention and on the film.

※ Explanation of code about main part of drawing ※

11 substrate 12 anode                 

13 hole transport layer 14 light emitting layer

15: electron transport layer 16: cathode

The present invention relates to an organic electroluminescent molecule containing 9,9-di (3,3'-bicarbazyl) -2,7-fluorenyl unit and an electroluminescent device using the same, and more particularly, to high solubility and Organic electro-molecules containing 9,9-di (3,3'-bicarbazyl) -2,7-fluorenyl unit having high thermal stability and improved hole transporting properties and high light emission efficiency, and electricity using the same It relates to a light emitting device.

Recently, due to the rapid growth of the optical communication and multimedia fields, the development into a highly information society has been accelerated. Accordingly, optoelectronic devices using the conversion of photons to electrons or the conversion of electrons to photons have become the core of the modern information electronics industry.

Such semiconductor optoelectronic devices can be broadly classified into electroluminescent devices, light receiving devices, and devices in which they are combined.

Until now, most displays are light-receiving, while self-emissive electroluminescence displays are fast response and self-emissive, so they don't need backlighting and have excellent brightness. It is attracting attention as a display element.                         

Such electroluminescent devices are classified into inorganic and organic light emitting devices according to materials for forming a light emitting layer.

Organic electroluminescence (EL) is a phenomenon in which when an electric field is applied to an organic material, electrons and holes are transferred from the cathode and the anode, respectively, to be combined within the material, and the energy generated is emitted as light. The electroluminescence of these organic materials was reported by Pope et al. In 1963, and in 1987 by Tang et al. At Eastmann Kodak, alumina-quinone. Many studies have been conducted since a light emitting device having a multilayer structure having a quantum efficiency of 1% and a luminance of 1000 cd / m 2 at 10 V or less as a device manufactured from a pigment having a π-conjugated structure. They have the advantage of easy synthesis and synthesis of various types of materials and simple color tuning. However, when the processability and thermal stability are low and the voltage is applied, Joule heat is generated in the light emitting layer, and as the molecules are rearranged, the device is destroyed and causes problems in the luminous efficiency or life of the device. Substitution is proceeding with the organic electroluminescent device having.

In this regard, FIG. 1 shows a structure of a general organic electroluminescent device made of a substrate / anode / hole transport layer / light emitting layer / electron transport layer / cathode.

Referring to FIG. 1, an anode 12 is formed on the substrate 11. The hole transport layer 13, the light emitting layer 14, the electron transport layer 15, and the cathode 16 are sequentially formed on the anode 12. Here, the hole transport layer 13, the light emitting layer 14, and the electron transport layer 15 are organic thin films made of an organic compound. The driving principle of the organic electroluminescent device of the above structure is as follows:

When a voltage is applied between the anode 12 and the cathode 16, holes injected from the anode 12 are moved to the light emitting layer 14 via the hole transport layer 13. On the other hand, electrons are injected into the light emitting layer 14 from the cathode 16 via the electron transport layer 15, and carriers are recombined in the light emitting layer 14 to generate excitons. This exciton is changed from the excited state to the ground state, whereby the fluorescent molecules of the light emitting layer emit light to form an image.

The organic electroluminescent device driven on the principle described above is classified into a polymer organic electroluminescent device and a low molecular organic electroluminescent device according to the molecular weight of the material for forming an organic film.

In general, in the case of using a low molecule in forming the organic film, the low molecule is easy to purify and can almost eliminate impurities, and excellent in luminescence properties. However, there is a problem that the spin coating is impossible and the heat resistance is poor, thereby deteriorating or recrystallization by the driving heat generated when the device is driven.

On the other hand, when the polymer is used to form the organic film, the energy level is separated into the conduction band and the electrical appliance diagram by the superposition of the π-electron wave function in the polymer backbone, and the band gap energy corresponding to the energy difference is used. The semiconducting properties of the polymer are determined and full color can be achieved. Such polymers are called π-conjugated polymers.

An electroluminescent device using poly (p-phenylenevinylene) (PPV), a polymer having conjugated double bonds, was first introduced in 1990 by a team of professors from RH Friend at the University of Cambridge, UK. After being announced, researches using organic polymers have been actively conducted. Compared with the low molecular weight polymer, the polymer has excellent heat resistance and can be spin coated to easily increase the size of the display device. By introducing various suitable substituents, polyphenylenevinylene (PPV) derivatives, polythiophene (Pth) derivatives, and the like, which can improve processability and express various colors, have been reported. However, as materials such as polyphenylenevinylene derivatives and polythiophene derivatives, high efficiency red and green light emitting polymer materials can be obtained among the three primary colors of light, but high efficiency blue light emitting polymer materials can be obtained. it's difficult.

In addition, polyphenylene derivatives, polyfluorene derivatives, and the like have been reported as blue light emitting polymer materials. Polyphenylene has high oxidation stability and thermal stability, but has a disadvantage of low luminous efficiency and poor solubility. On the other hand, polyfluorene derivatives have been researched the most with blue ad molecules, but still have problems such as minimizing the interaction between excitons produced in one molecule and the excitons of other molecules, improving efficiency, and improving lifetime. In particular, in order to manufacture high-efficiency devices using polyfluorene derivatives, improvement of hole injection and delivery properties is required.

Therefore, in the present invention, as a result of extensive research in order to solve the above problems, it has excellent thermal stability, has good solubility and minimizes intermolecular interaction while improving hole injection and delivery properties and high luminous efficiency. In addition, the present inventors have found an electro-molecule having a 3,3'-bicarbazyl group di-substituted in the 9-position and an electroluminescent device using the same. The present invention has been completed based on this.

Accordingly, an object of the present invention is to minimize the intermolecular interaction, to facilitate energy transfer, to minimize the vibration mode (vibronic mode) and to improve the injection and transfer properties of the excellent luminous efficiency with high thermal and oxidative stability The present invention provides an organic electrobalancing molecule to be expressed.

Another object of the present invention is to provide an electroluminescent device manufactured using the organic electroluminescent molecules.

The 9,9-di (3,3'-bicarbazyl) -2,7-fluorenyl unit-containing organic electroadhesive molecule according to the present invention for achieving the above object is a 3,3 in the 9-position of fluorene It is characterized by represented by the following formula (1), introduced '-dicarbazyl group:

Wherein R ₁ , R ₂ and R ₃ are the same as or different from each other, or an alkyl group having 1 to 20 carbon atoms, an aryl group substituted with an alkyl group having 1 to 20 carbon atoms, at least one of F, S, N, O, P and Si atoms Containing a C1-C20 alkyl group containing one hetero atom or a C2-C24 heterocycle containing at least one hetero atom of F, S, N, O, P and Si atoms An aryl group, an aryl group including a heterocycle including an alkyl group having 1 to 20 carbon atoms or an alkoxy group, a trialkylsiloxy group of C3 to C40, or an arylsilyl group which is unsubstituted or substituted with C3 to C40 alkyl; a and b are each the same as or different from each other and are integers of 1 to 3; Ar is a C6 to C26 aromatic group or a C2 to C14 heterocyclic aromatic group in which at least one hetero atom of N, S, O, P and Si atoms is included in the aromatic ring, wherein the aromatic group and heterocyclic aromatic group are vinyl A group, an alkyl group having 1 to 16 carbon atoms or an alkoxy group, a silyl group and an amine group; And l is an integer of 1 to 100,000, m is an integer of 0 to 100,000, and n is an integer of 1 to 100,000.

The organic electroluminescent device according to the present invention for achieving the above another object is characterized by using the organic electroluminescent advertising molecule as a material for forming a hole transport layer, a light emitting layer or an electron transport layer.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.                     

As described above, in the present invention, 9,9-di (3,3'-bicarbazyl) -2,7-fluore, which has high solubility and high thermal stability and has improved hole transporting properties, exhibiting high luminous efficiency. Provided are an organic electroluminescent molecule containing a neil unit and an electroluminescent device using the same.

The organic electro-adhesive molecule according to the present invention is a 3,3'-bicarba which is a large substituent at the 9-position of fluorene used as the main chain as a material having excellent thermal stability, light stability, solubility, film formability and high quantum efficiency. By introducing the toughness, the arrangement between the main chain and the substituent becomes random, and the characteristic that the intermolecular excimer is suppressed by the substituent is expressed as much as possible, which is one of the biggest problems of polyfluorenes. Formation of aggregation and / or excimer is extremely suppressed, and intermolecular or intermolecular energy transfer from the 3,3'-bicarbazyl group, which is a substituent that exhibits light emission in the short wavelength band, is possible. In addition, the 9-position of the fluorene group used as the main chain is suppressed in the rotation and vibration mode by the substituted 3,3'-bicarbazyl group, which greatly reduces nonradiative decay. Since the 3,3'-bicarbazyl group assists the injection and transfer of holes, the organic electroluminescent molecule of the present invention exhibits excellent color purity, brightness, and high efficiency.

The organic electroadhesion molecule containing 9,9-di (3,3'-bicarbazyl) -2,7-fluorenyl unit according to the present invention is represented by the following general formula (1):                     

Formula 1

Wherein R ₁ , R ₂ and R ₃ are the same as or different from each other, or an alkyl group having 1 to 20 carbon atoms, an aryl group substituted with an alkyl group having 1 to 20 carbon atoms, at least one of F, S, N, O, P and Si atoms Containing a C1-C20 alkyl group containing one hetero atom or a C2-C24 heterocycle containing at least one hetero atom of F, S, N, O, P and Si atoms An aryl group, an aryl group including a heterocycle including an alkyl group having 1 to 20 carbon atoms or an alkoxy group, a trialkylsiloxy group of C3 to C40, or an arylsilyl group which is unsubstituted or substituted with C3 to C40 alkyl; a and b are each the same as or different from each other and are integers of 1 to 3; Ar is a C6 to C26 aromatic group or a C2 to C14 heterocyclic aromatic group in which at least one hetero atom of N, S, O, P and Si atoms is included in the aromatic ring, wherein the aromatic group and heterocyclic aromatic group are vinyl A group, an alkyl group having 1 to 16 carbon atoms or an alkoxy group, a silyl group and an amine group; And l is an integer of 1 to 100,000, m is an integer of 0 to 100,000, and n is an integer of 1 to 100,000.

Preferably, R ₁ is selected from the following compounds:

Preferably, R ₂ and R ₃ are each the same or differently selected from the following compounds:

Preferably, Ar is selected from the following compounds:

Here, R ₄ and R ₅ are the same as or different from each other, or an alkyl or alkoxy group having 1 to 20 carbon atoms, or an aryl group or unsubstituted aryl group having 4 to 24 carbon atoms substituted with them.

Preferably, the organic electroadhesive molecule according to the present invention is a compound represented by the following Chemical Formula 2:

Wherein n is an integer of 1 to 100,000.

One of the methods for preparing the organic electro-molecular advertising molecule of the present invention is as follows. That is, after preparing monomers through alkylation reaction, bromination reaction, Grignard reaction, Wittig reaction, etc., organic electroadhesive molecules may be finally prepared through CC coupling reaction such as Yamamoto coupling reaction and Suzuki coupling reaction. Can be. The number average molecular weight of the polymers obtained therefrom is 700 to 10,000,000, and the molecular weight distribution is 1 to 100.

The organic electro-adhesive molecules according to the present invention described above can not only significantly improve the injection and delivery of holes, which are disadvantages of the conventional polyfluorene-based (PFs), but also have excellent thermal stability, oxidation stability and solubility, and intermolecular. The interaction is minimized, the energy transfer is easy, and the vibration mode is suppressed to the maximum, thereby exhibiting high light emission characteristics.                     

According to the present invention, the organic electroluminescent molecule is used as a material for forming a light emitting layer, a hole transport layer or an electron transport layer located between a pair of electrodes in the electroluminescent device.

The organic electroluminescent device of the present invention may be configured to further include a hole transport layer and an electron transport layer as well as the most common device configuration of the anode / light emitting layer / cathode.

1 is a cross-sectional view illustrating a structure of a general organic electroluminescent device composed of a substrate / anode / hole transport layer / light emitting layer / electron transport layer / cathode. Referring to this, an example of an organic electroluminescent device to which the organic electroluminescent molecule of the present invention is applied is as follows. It can be prepared as follows.

First, a material for the anode 12 electrode is coated on the substrate 11.

Here, the substrate 11 is a substrate used in a conventional organic electroluminescent device, preferably a glass substrate or a transparent plastic substrate excellent in transparency, surface smoothness, ease of handling and waterproof.

In addition, as the material for the anode 12 electrode, indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), or the like, which is transparent and has excellent conductivity, may be used.

Next, the hole transport layer 13 may be formed by vacuum deposition or sputtering on the anode 11 electrode, and the light emitting layer 14 may be formed by spin coating. In addition, the electron transport layer 15 is formed on the light emitting layer 14 before the cathode 16 is formed. In this case, the thickness of the light emitting layer 14 may be 10 to 10,000 kPa, and the thickness of the hole transport layer 13 and the electron transport layer 15 may be 10 to 10,000 kPa.

According to the present invention, a material for forming an electron transport layer may be used for the electron transport layer 15, or the compound represented by Chemical Formula 1 may be formed by vacuum deposition or spin coating.

The hole transport layer 13 and the electron transport layer 15 serves to increase the probability of light emitting coupling in the light emitting polymer by efficiently transporting the carriers to the light emitting polymer. The material for forming the hole transport layer 13 and the electron transport layer 15 usable in the present invention is not particularly limited, but preferably, the material for the hole transport layer 13 is a poly (doped with a poly (styrenesulphonic acid) (PSS) layer. PEDOT: PSS, N, N'-bis (3-methylphenyl) -N, N-diphenyl- [1,1'-biphenyl] -4, which is 3,4-ethylenedioxy-thiophene) (PEDOT), 4'-diamine (TPD) is preferred, and as an electron transport layer material, aluminum trihydroxyquinoline (Alq3), 1,3,4-oxadiazole derivative PBD (2- (4-biphenylyl) -5- phenyl-1,3,4-oxadiazole, TPQ (1,3,4-tris [(3-penyl-6-trifluoromethyl) quinoxaline-2-yl] benzene), which is a quinoxaline derivative, and a triazole derivative.

Optionally, a hole-blocking layer, such as lithium fluoride (LiF), is further formed by vacuum deposition or the like to limit the transfer rate of holes in the light-emitting layer 14 and to bond electron-holes. You can increase the probability.

Finally, a material for the cathode 16 electrode is coated on the electron transport layer 15.

As the cathode forming metal, lithium (Li), magnesium (Mg), aluminum (Al), Al: Li, calcium (Ca) and the like having a small work function are used.

The organic electroluminescent device according to the present invention may be manufactured in the order as described above, namely anode / hole transport layer / light emitting layer / electron transport layer / cathode, and vice versa, that is, cathode / electron transport layer / light emitting layer / hole transport layer / anode You may manufacture in order.

As described above, the organic electroluminescent molecules according to the present invention are materials having excellent thermal stability, light stability, solubility, film formability and high quantum efficiency, and the formation of aggregation and / or excimer is extremely suppressed. Intra-molecular or intermolecular energy transfer from the 3,3'-bicarbazyl group, which is a substituent showing light emission in the short wavelength band, to the main slot is possible. In addition, the organic electro-adhesive molecule of the present invention has a 9-position of the fluorene group used as the main chain because the rotational and vibrational modes are suppressed by the substituted large 3,3'-bicarbazyl group, thereby greatly reducing the non-radioactive decay. It exhibits excellent color purity, brightness and high efficiency light emission characteristics.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited thereto.

The following Examples 1 to 5 were carried out according to the reaction overview shown in FIG.

Example 1

-Synthesis of (N- (2-ethyl) hexyl carbazole (1)

20.0 g of carbazole and 23.1 g of 1-bromo-2-ethyl hexane were dissolved in a 250 mL round flask, and 150 mL of DMSO was dissolved. Then, 16.1 g of potassium t-butoxide was slowly injected at room temperature and stirred at room temperature for 24 hours. do. 500 ml of water was added to the reaction mixture, followed by extraction with diethyl ether, drying with MgSO ₄ , solvent removal with a rotary evaporator, and column chromatography using hexane to separate the compound (1). ) 27.7 g (83%).

Example 2

-Synthesis of (3-bromo-N- (2-ethyl) hexyl carbazole (2)

After dissolving 20 g of Compound (1) in 200 ml of DMF in a 500 ml round flask, the temperature was lowered to 0 ° C., and a solution of 12.7 g of N-bromosuccinimide in 80 ml of DMF was slowly added while stirring, The reaction is carried out at 0 ° C. for 4 hours. 150 ml of water is poured into the reaction to terminate the reaction. The mixture is extracted with diethyl ether and the solvent is blown on a rotary evaporator. The mixture was separated by column chromatography using hexane to give 23.6 g (93%) of compound (2).

Example 3

-Synthesis of (N, N-di (2-ethyl) hexyl-3,3'-carbazyl) (3)

In a 500 ml round flask, 0.50 g of NiCl ₂ , 0.68 g of BPY (bipyridyl), 11.44 g of triphenylphosphine (PPh ₃ ), and 11.12 g of Zn were added and dissolved in 100 ml of DMF. Raise and stir for 1 hour. Compound (2) was dissolved in 100 ml of DMF and injected into the prepared catalyst system, followed by reaction at 90 ° C. for 24 hours with stirring. After the reaction was cooled to room temperature, 150 ml of water was poured out to terminate the reaction. The mixture was extracted with diethyl ether and the solvent was blown with a rotary evaporator. The mixture was separated by column chromatography using hexane to give 9.3 g (62%) of compound (3).

Example 4

-Synthesis of (9,9-bis (N, N-bi (2-ethyl) hexyl-3,3'-carbazyl) -2,7-dibromo fluorine) (4)

17.2 g of compound (3), 0.74 g of 2,7-dibromofluorene-9-one and 0.21 g of methanesulphonic acid were added to a 50 ml round flask, and reacted at 140 ° C. for 48 hours. 100 mL of water was added thereto, extracted with diethyl ether, and the residue was separated by column chromatography using hexane and ethyl acetate to obtain 9.3 g (62%) of compound (4). ¹ H-NMR spectrum of Compound (4) obtained therefrom is shown in FIG. 3.

Example 5

-Synthesis of Poly (9,9-bis (N, N-bi (2-ethyl) hexyl-3,3'-carbazyl) -2,7-fluorenyl) (Formula 2)

1 g (0.7 mmol) of Compound (4) was added to a 100 ml Schlenk flask, dissolved in 10 ml of toluene degassed with nitrogen, and stored under nitrogen. As a catalyst, 0.44 g (1.6 mmol) of Ni (COD) ₂ , 0.11 g (1.1 mmol) of 1.4-cyclooctadiene (COD) and 0.25 g (1.6 mmol) of dipyridyl were added to a Schlenk flask under nitrogen, followed by nitrogen. 3 ml of degassed toluene and 3 ml of DMF were added, followed by stirring at 80 ° C. for 30 minutes. The monomer solution prepared above was added to the reaction vessel, and reacted for 24 hours, 2 ml of bromobenzene was added, followed by reaction for 24 hours to terminate the terminal. After the reaction was completed, the reaction solution was added to 150 ml of hydrochloric acid (35 wt%): acetone: ethanol = 1: 1: 1 solution to remove the unreacted catalyst and to precipitate a polymer. After filtering the polymer was dissolved in chloroform and filtered again with celite to remove the residual catalyst, concentrated and reprecipitated in methanol and washed with Soxhlet for 24 hours. Molecular weight: Mw = 60,000, PDI = 3.9. ¹ H-NMR spectrum of the compound represented by Chemical Formula 2 obtained therefrom is shown in FIG. 4. In addition, the fluorescence spectrum on the chloroform solution and the film of the compound of Formula 2 is shown in FIG.

Referring to the film fluorescence spectrum shown in Figure 5, it was confirmed that the peak by the excimer around 530nm which is a problem of the conventional polyfluorene did not appear, which is the luminous efficiency of the device using the compound of formula 2 and It suggests that device life can be greatly improved.

As described above, the electro-adhesive molecule according to the invention has a high solubility and high thermal stability by introducing a 3,3'-bicarbasil (3,3 ') group at the 9-position of fluorene, and improves the hole transporting property. It exhibits excellent light emission characteristics when applied to a host material as an electroluminescent device.

Claims (4)

9,9-di (3,3'-bicarbazyl) -2,7-fluore, represented by the following Chemical Formula 1, having introduced a 3,3'-dicarbazyl group at the 9-position of fluorene: Organic Electroplating Molecules Containing Neal Units: Formula 1

Wherein R ₁ , R ₂ and R ₃ are the same as or different from each other, or an alkyl group having 1 to 20 carbon atoms, an aryl group substituted with an alkyl group having 1 to 20 carbon atoms, at least one of F, S, N, O, P and Si atoms Containing a C1-C20 alkyl group containing one hetero atom or a C2-C24 heterocycle containing at least one hetero atom of F, S, N, O, P and Si atoms An aryl group, an aryl group including a heterocycle including an alkyl group having 1 to 20 carbon atoms or an alkoxy group, a trialkylsiloxy group of C3 to C40, or an arylsilyl group which is unsubstituted or substituted with C3 to C40 alkyl; a and b are each the same as or different from each other and are integers of 1 to 3; Ar is a C6 to C26 aromatic group or a C2 to C14 heterocyclic aromatic group in which at least one hetero atom of N, S, O, P and Si atoms is included in the aromatic ring, wherein the aromatic group and heterocyclic aromatic group are vinyl A group, an alkyl group having 1 to 16 carbon atoms or an alkoxy group, a silyl group and an amine group; And l is an integer of 1 to 100,000, m is an integer of 0 to 100,000, and n is an integer of 1 to 100,000. According to claim 1, wherein the organic electro-adsorption molecule has an average molecular weight of 700 to 10,000,000, the molecular weight distribution of the organic electro-adhesion molecule, characterized in that 1 to 100. An organic electroluminescent device using the organic electroluminescent advertising molecule according to claim 1 as a material for forming a hole transport layer, a light emitting layer or an electron transport layer. The organic electroluminescent device according to claim 3, wherein the structure of the electroluminescent device is an anode / light emitting layer / cathode, an anode / hole transporting layer / light emitting layer / cathode, or an anode / hole transporting layer / light emitting layer / electron transporting layer / cathode.

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